System and method for communicating using bandwidth on demand

ABSTRACT

A system and method for dynamically changing the quality of service (QoS) for a subscriber of a cellular radio system. Bandwidth-on-Demand (BoD) enables the subscriber to dynamically switch to higher bandwidth and to enable a higher throughput. This may be for a limited time or amount of data, for example. The initiation may be by the subscriber, carrier, sponsor, or automatically by an application. The QoS increase may be dynamically priced in a kind of auction. The wireless device may contact the policy servers of a multiple network operator (MNO), which in turn contacts the Authentication, Authorization and Accounting (AAA) server in the MNO&#39;s core network. The policy server contacts the scheduler on the serving basestation which then determines whether to allocate more resources (i.e. bandwidth in the form of subcarriers, resource blocks, resource elements, timeslots) to the subscriber. The initiation may start a timer or data counter.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims benefit of priority from U.S. ProvisionalPatent Application Ser. No. 61/555,585, filed Nov. 4, 2011, the entiretyof which is expressly incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to the field of wireless communications ofradio-frequency signals. More specifically, it relates to communicationssystems and methods which provide bandwidth in excess of that availablein a single normal communication channel to a receiver.

BACKGROUND OF THE INVENTION

It is known to “bond” multiple communication channels together toprovide increased data bandwidth. For example, ISDN supports aggregatingdata in multiple “B” (bearer) channels into a composite stream.Likewise, h.320 videoconferencing coordinates multiple ISDN channels.

Similarly, it is known to aggregate bandwidth in multiple channelswithin an IEEE-802.11g (called “super-g” or “turbo-g”, for nominal 108or 125 megabits per second communications, instead of the normal peak 54megabits per second available for a single channel), or 802.11n or802.11ac communication for even higher data rates.

An issue arises when communicating multiple modulated data streamsthrough a common amplifier. Each modulated signal has a peak to averagepower ratio. The lower the ratio, the more efficiently the poweramplifier of the transmitter can operate, and, given legal or practicallimits on maximum transmit power, the greater the communication range orbandwidth. When multiple streams are combined, it is possible for thepeak signal to double, leading to a requirement for an amplifier havingdouble the peak power, or limiting the power of each component to lessthan the normal maximum. Therefore, significant inefficiencies may arisewhen multiple modulated signals are merely summed before the poweramplifier, and seeking to sum after the power amplifier also createsproblems.

On the other hand, if instead of the multiple modulated signals, asingle data stream is provided, backwards compatibility of the systemwith normal users of the communication channel might be impaired.

Therefore, from a transmit perspective, it is difficult to increase theeffective bandwidth of a system by bonding two wireless channels havinglegacy protocol together, while maintaining efficiency and backwardscompatibility.

A common signal format for mobile wireless communications is orthogonalfrequency-domain multiplexing, or OFDM, and closely related formats suchas orthogonal frequency-domain multiple access (OFDMA). For a signalconveyed on an OFDM channel, this is characterized in the frequencydomain by a bundle of narrow adjacent subchannels, and in the timedomain by a relatively slow series of OFDM symbols each with a time T,each separated by a guard interval ΔT (see FIG. 1). Within the guardinterval before each symbol is a cyclic prefix (CP), comprised of thesame signal in the symbol period, cyclically shifted in time. This CP isdesigned to reduce the sensitivity of the received signal to precisetime synchronization in the presence of multipath, i.e., radio-frequencysignals reflecting from large objects in the terrain such as tallbuildings, hills, etc. If a given symbol is received with a slight timedelay (less than ΔT), it will still be received without error. Inaddition to the data symbols associated with the OFDM “payload”, thereis also typically a “preamble” signal that establishes timing and otherstandards. The preamble may have its own CP, not shown in FIG. 1.

In OFDM, the sub-carrier frequencies are chosen so that the sub-carriersare orthogonal to each other, meaning that cross-talk between thesub-channels is eliminated and inter-sub-carrier guard bands are notrequired. This greatly simplifies the design of both the transmitter andthe receiver; unlike conventional FDM, a separate filter for eachsub-channel is not required. The orthogonality requires that thesub-carrier spacing is Δf=k/(T_(U)) Hertz, where T_(U) seconds is theuseful symbol duration (the receiver side window size), and k is apositive integer, typically equal to 1. Therefore, with N sub-carriers,the total passband bandwidth will be B≈N·Δf (Hz). The orthogonality alsoallows high spectral efficiency, with a total symbol rate near theNyquist rate. Almost the whole available frequency band can be utilized.OFDM generally has a nearly “white” spectrum, giving it benignelectromagnetic interference properties with respect to other co-channelusers.

When two OFDM signals are combined, the result is in general anon-orthogonal signal. While a receiver limited to the band of a singleOFDM signal would be generally unaffected by the out-of-channel signals,when such signals pass through a common power amplifier, there is aninteraction, due to the inherent nonlinearities of the analog systemcomponents.

OFDM requires very accurate frequency synchronization between thereceiver and the transmitter; with frequency deviation the sub-carrierswill no longer be orthogonal, causing inter-carrier interference (ICI),i.e. cross-talk between the sub-carriers. Frequency offsets aretypically caused by mismatched transmitter and receiver oscillators, orby Doppler shift due to movement. While Doppler shift alone may becompensated for by the receiver, the situation is worsened when combinedwith multipath, as reflections will appear at various frequency offsets,which is much harder to correct.

The orthogonality allows for efficient modulator and demodulatorimplementation using the fast Fourier transform (FFT) algorithm on thereceiver side, and inverse FFT (IFFT) on the sender side. While the FFTalgorithm is relatively efficient, it has modest computationalcomplexity which may be a limiting factor.

One key principle of OFDM is that since low symbol rate modulationschemes (i.e. where the symbols are relatively long compared to thechannel time characteristics) suffer less from intersymbol interferencecaused by multipath propagation, it is advantageous to transmit a numberof low-rate streams in parallel instead of a single high-rate stream.Since the duration of each symbol is long, it is feasible to insert aguard interval between the OFDM symbols, thus eliminating theintersymbol interference. The guard interval also eliminates the needfor a pulse-shaping filter, and it reduces the sensitivity to timesynchronization problems.

The cyclic prefix, which is transmitted during the guard interval,consists of the end of the OFDM symbol copied into the guard interval,and the guard interval is transmitted followed by the OFDM symbol. Thereason that the guard interval consists of a copy of the end of the OFDMsymbol is so that the receiver will integrate over an integer number ofsinusoid cycles for each of the multipaths when it performs OFDMdemodulation with the FFT.

The effects of frequency-selective channel conditions, for examplefading caused by multipath propagation, can be considered as constant(flat) over an OFDM sub-channel if the sub-channel is sufficientlynarrow-banded, i.e. if the number of sub-channels is sufficiently large.This makes equalization far simpler at the receiver in OFDM incomparison to conventional single-carrier modulation. The equalizer onlyhas to multiply each detected sub-carrier (each Fourier coefficient) bya constant complex number, or a rarely changed value. Therefore,receivers are generally tolerant of such modifications of the signal,without requiring that explicit information be transmitted.

OFDM is invariably used in conjunction with channel coding (forwarderror correction), and almost always uses frequency and/or timeinterleaving. Frequency (subcarrier) interleaving increases resistanceto frequency-selective channel conditions such as fading. For example,when a part of the channel bandwidth is faded, frequency interleavingensures that the bit errors that would result from those subcarriers inthe faded part of the bandwidth are spread out in the bit-stream ratherthan being concentrated. Similarly, time interleaving ensures that bitsthat are originally close together in the bit-stream are transmitted farapart in time, thus mitigating against severe fading as would happenwhen travelling at high speed. Therefore, similarly to equalization perse, a receiver is typically tolerant to some degree of modifications ofthis type, without increasing the resulting error rate.

The OFDM signal is generated from the digital baseband data by aninverse (fast) Fourier transform (IFFT), which is computationallycomplex, and as will be discussed below, generates a resulting signalhaving a relatively high peak to average power ratio (PAPR) for a setincluding a full range of symbols. This high PAPR, in turn generallyleads to increased acquisition costs and operating costs for the poweramplifier (PA), and typically a larger non-linear distortion as comparedto systems designed for signals having a lower PAPR. This non-linearityleads, among other things, to clipping distortion and intermodulation(IM) distortion, which have the effect of dissipating power, causing outof band interference, and possibly causing in-band interference with acorresponding increase in bit error rate (BER) at a receiver.

In a traditional type OFDM transmitter, a signal generator performserror correction encoding, interleaving, and symbol mapping on an inputinformation bit sequence to produce transmission symbols. Thetransmission symbols are subjected to serial-to-parallel conversion atthe serial-to-parallel (S/P) converter and converted into multipleparallel signal sequences. The S/P converted signal is subjected toinverse fast Fourier transform at IFFF unit. The signal is furthersubjected to parallel-to-serial conversion at the parallel-to-serial(P/S) converter, and converted into a signal sequence. Then, guardintervals are added by the guard interval (GI) adding unit. Theformatted signal is then up-converted to a radio frequency, amplified atthe power amplifier, and finally transmitted as an OFDM signal by aradio antenna.

On the other hand, in a traditional type of the OFDM receiver, the radiofrequency signal is down-converted to baseband or an intermediatefrequency, and the guard interval is removed from the received signal atthe guard interval removing unit. Then, the received signal is subjectedto serial-to-parallel conversion at S/P converter, fast Fouriertransform at the fast Fourier transform (FFT) unit, andparallel-to-serial conversion at P/S converter. Then, the decoded bitsequence is output.

It is conventional for each OFDM channel to have its own transmit chain,ending in a power amplifier (PA) and an antenna element. However, insome cases, one may wish to transmit two or more separate OFDM channelsusing the same PA and antenna, as shown in FIG. 2. This may permit asystem with additional communications bandwidth on a limited number ofbase-station towers. Given the drive for both additional users andadditional data rate, this is highly desirable. The two channels may becombined at an intermediate frequency using a two-stage up-conversionprocess as shown in FIG. 2. Although amplification of real basebandsignals is shown in FIG. 2, in general one has complex two-phase signalswith in-phase and quadrature up-conversion (not shown). FIG. 2 also doesnot show the boundary between digital and analog signals. The basebandsignals are normally digital, while the RF transmit signal is normallyanalog, with digital-to-analog conversion somewhere between thesestages.

Consider two similar channels, each with average power P₀ and maximuminstantaneous power P₁. This corresponds to a peak-to-average powerratio PAPR=P₁/P₀, usually expressed in dB as PAPR[dB]=10 log(P₁/P₀). Forthe combined signal, the average power is 2 P₀ (an increase of 3 dB),but the maximum instantaneous power can be as high as 4 P₁, an increaseof 6 dB. Thus, PAPR for the combined signal can increase by as much as 3dB. This maximum power will occur if the signals from the two channelshappen to have peaks which are in phase. This may be a rare transientoccurrence, but in general the linear dynamic range of all transmitcomponents must be designed for this possibility. Nonlinearities willcreate intermodulation products, which will degrade the signal and causeit to spread into undesirable regions of the spectrum. This, in turn,may require filtering, and in any case will likely reduce the powerefficiency of the system.

Components with required increases in linear dynamic range to handlethis higher PAPR include digital-to-analog converters, for example,which must have a larger number of effective bits to handle a largerdynamic range. But even more important is the power amplifier (PA),since the PA is generally the largest and most power-intensive componentin the transmitter. While it is sometimes possible to maintaincomponents with extra dynamic range that is used only a small fractionof the time, this is wasteful and inefficient, and to be avoided wherepossible. An amplifier with a larger dynamic range typically costs morethan one with a lower dynamic range, and often has a higher quiescentcurrent drain and lower efficiency for comparable inputs and outputs.

This problem of the peak-to-average power ratio (PAPR) is a well-knowngeneral problem in OFDM and related waveforms, since they areconstructed of multiple closely-spaced subchannels. There are a numberof classic strategies to reducing the PAPR, which are addressed in suchreview articles as “Directions and Recent Advances in PAPR ReductionMethods”, Hanna Bogucka, Proc. 2006 IEEE International Symposium onSignal Processing and Information Technology, pp. 821-827, incorporatedherein by reference. These PAPR reduction strategies include amplitudeclipping and filtering, coding, tone reservation, tone injection, activeconstellation extension, and multiple signal representation techniquessuch as partial transmit sequence (PTS), selective mapping (SLM), andinterleaving. These techniques can achieve significant PAPR reduction,but at the expense of transmit signal power increase, bit error rate(BER) increase, data rate loss, increase in computational complexity,and so on. Further, many of these techniques require the transmission ofadditional side-information (about the signal transformation) togetherwith the signal itself, in order that the received signal be properlydecoded. Such side-information reduces the generality of the technique,particularly for a technology where one would like simple mobilereceivers to receive signals from a variety of base-stationtransmitters. To the extent compatible, the techniques disclosed inBogucka, and otherwise known in the art, can be used in conjunction withthe techniques discussed herein-below.

Various efforts to solve the PAPR (Peak to Average Power Ratio) issue inan OFDM transmission scheme, include a frequency domain interleavingmethod, a clipping filtering method (See, for example, X. Li and L. J.Cimini, “Effects of Clipping and Filtering on the Performance of OFDM”,IEEE Commun. Lett., Vol. 2, No. 5, pp. 131-133, May, 1998), a partialtransmit sequence (PTS) method (See, for example, L. J Cimini and N. R.Sollenberger, “Peak-to-Average Power Ratio Reduction of an OFDM SignalUsing Partial Transmit Sequences”, IEEE Commun. Lett., Vol. 4, No. 3,pp. 86-88, March, 2000), and a cyclic shift sequence (CSS) method (See,for example, G. Hill and M. Faulkner, “Cyclic Shifting and TimeInversion of Partial Transmit Sequences to Reduce the Peak-to-AverageRatio in OFDM”, PIMRC 2000, Vol. 2, pp. 1256-1259, September 2000). Inaddition, to improve the receiving characteristic in OFDM transmissionwhen a non-linear transmission amplifier is used, a PTS method using aminimum clipping power loss scheme (MCPLS) is proposed to minimize thepower loss clipped by a transmission amplifier (See, for example, XiaLei, Youxi Tang, Shaoqian Li, “A Minimum Clipping Power Loss Scheme forMitigating the Clipping Noise in OFDM”, GLOBECOM 2003, IEEE, Vol. 1, pp.6-9, December 2003). The MCPLS is also applicable to a cyclic shiftingsequence (CSS) method.

In a partial transmit sequence (PTS) scheme, an appropriate set of phaserotation values determined for the respective subcarriers in advance isselected from multiple sets, and the selected set of phase rotations isused to rotate the phase of each of the subcarriers before signalmodulation in order to reduce the peak to average power ratio (See, forexample, S. H. Muller and J. B. Huber, “A Novel Peak Power ReductionScheme for OFDM”, Proc. of PIMRC '97, pp. 1090-1094, 1997; and G. R.Hill, Faulkner, and J. Singh, “Deducing the Peak-to-Average Power Ratioin OFDM by Cyclically Shifting Partial Transmit Sequences”, ElectronicsLetters, Vol. 36, No. 6, 16^(th) March, 2000).

What is needed is a practical method and associated apparatus forreducing the PAPR of combined OFDM signals, in a way that does notdegrade the received signal or require the transmission ofside-information.

The following patents, each of which are expressly incorporated hereinby reference, relate to peak power ratio considerations: U.S. Pat. Nos.7,535,950; 7,499,496; 7,496,028; 7,467,338; 7,463,698; 7,443,904;7,376,202; 7,376,074; 7,349,817; 7,345,990; 7,342,978; 7,340,006;7,321,629; 7,315,580; 7,292,639; 7,002,904; 6,925,128; 7,535,950;7,499,496; 7,496,028; 7,467,338; 7,443,904; 7,376,074; 7,349,817;7,345,990; 7,342,978; 7,340,006; 7,339,884; 7,321,629; 7,315,580;7,301,891; 7,292,639; 7,002,904; 6,925,128; 5,302,914; 20100142475;20100124294; 20100002800; 20090303868; 20090238064; 20090147870;20090135949; 20090110034; 20090110033; 20090097579; 20090086848;20090080500; 20090074093; 20090067318; 20090060073; 20090060070;20090052577; 20090052561; 20090046702; 20090034407; 20090016464;20090011722; 20090003308; 20080310383; 20080298490; 20080285673;20080285432; 20080267312; 20080232235; 20080112496; 20080049602;20080008084; 20070291860; 20070223365; 20070217329; 20070189334;20070140367; 20070121483; 20070098094; 20070092017; 20070089015;20070076588; 20070019537; 20060268672; 20060247898; 20060245346;20060215732; 20060126748; 20060120269; 20060120268; 20060115010;20060098747; 20060078066; 20050270968; 20050265468; 20050238110;20050100108; 20050089116; and 20050089109.

See, also, each of which is expressly incorporated herein by reference:

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SUMMARY OF THE INVENTION

The world today is about smart connectivity. Smartphones, tablets,netbooks, and computers form a key component in the connected world.Smart connectivity hinges on the concept of “any-time; any-where”, ameans by which users can access content across various sources on thego. Mobile network operators (MNO) play a vital role in advancement ofsmart connectivity. MNOs provide the bridge between the content and thedevice, and hence, in many countries they also act as key point-of-salefor the distribution of the mobile devices like Smartphones, Tabletsetc. The devices usually come with a data plan that is tied to themonthly fee paid by the subscriber. Data plans are usually fixed andcapped to a limit, though some operators do provide anall-you-can-consume data plan. Such data plans are not flexible, and donot provide any ability of the user to change the plan dynamically.Moreover, most data plans do not specify the speed at which the data isdelivered. Applications like video and gaming not only require hugedata, they also require them to the delivered fast, i.e. delivered at ahigher data rate. Data plans today do not require you to specify anyminimum throughput at which the data is delivered. Data delivery istaken care by the quality-of-service (QoS) parameters and it is verydifficult for the subscriber to change the QoS dynamically, or to changethe throughput. With this invention we provide a method for thesubscriber to dynamically change the QoS and hence move to a higherthroughput as mandated and required by the subscriber or device.

An embodiment of the present technology, called Bandwidth-on-Demand(BoD), enables the subscriber of the mobile device to dynamically switch(or be switched) to higher bandwidth and to enable a higher throughput,which may be for a fixed period of time. For example, upon expiry ofthat period, the device reverts to its original throughput, as per thesubscriber's plan.

See, e.g., U.S. Pat. No. 7,643,489, U.S. Pat. No. 6,738,348, and U.S.Pat. No. 5,828,737, each of which is expressly incorporated herein byreference.

Yieh-Ran Haung; Yi-Bing Lin; “A bandwidth-on-demand strategy for GPRS”,IEEE Trans. Wireless Communications, (July 2005), 4 (4):1394-1399,expressly incorporated herein by reference, discusses that Generalpacket radio service (GPRS) is a global system for mobile communications(GSM) packet data service. It proposes that, in order to efficientlyaccommodate GPRS traffic while maintaining the desired service qualityof GSM calls, a GPRS BoD bandwidth-allocation strategy, adaptive to thechange of traffic conditions, and thus dynamically adjusting the numberof channels for GSM and GPRS traffic be employed.

Cisco Turbo Boost for Mobile Broadband,www.cisco.com/en/US/solutions/collateral/ns341/ns973/ns1081/brochure_c02-620391.html,suggests that subscribers sometimes want the ability to upgrade theperformance of certain high-bandwidth applications for a specific timeperiod, and that operators can gain additional revenue by offering usersthe ability to turbo-boost application performance on demand. Forexample, the mobile operator might detect that a subscriber to itslowest-tier pricing plan is playing an online gaming application. Duringthe session, the operator offers the user the ability to increaseavailable bandwidth for the remainder of the gaming session, and theuser, who really wants to win the game, accepts the additional chargefor the Turbo Boost. Optionally, operators might also expose a networkAPI for over-the-top (OTT) application providers who can bundle in anoperator network-enabled “turbo boost” capability in theirbandwidth-intensive services, to ensure a satisfactory user experiencewhile sharing revenue with the operator. The feature providessubscribers the opportunity to purchase on-demand upgrades to quality ofservice (QoS) when accessing specific high-bandwidth applications. Thefeature allows users to dynamically improve performance of anapplication at the time of its usage, and permits business models forapplication providers to embed the turbo boost capability into theirservices on an as-needed burst basis to ensure quality of the userexperience. Cisco proposes that this would gain new revenues from usersupgrading QoS on demand for applications of their choice. For example,an operator could offer a user playing a massively multiplayer online(MMO) game or watching a streaming high-definition video a bandwidthspeed upgrade for the session; creating higher uptake rate for serviceupgrades when offered dynamically “in service”. It also provides anexposed API for OTT application providers, increasing operator'spartnership revenue opportunities. The feature is delivered using theCisco® ASR 5000, and utilizes several In-line Services functions such asEnhanced Charging Service, Application Detection and Control, TrafficOptimization, and Policy Enforcement. It may be used in conjunction withCisco Mobility Unified Reporting, to provide statistical analysis andtrending information of network attributes and subscriber sessions,using deep packet inspection (DPI) capabilities of the Cisco ASR 5000and the Cisco Policy and Charging Control (PCC), to enable users tochoose to upgrade quality of service dynamically, or in the case ofbundled capability, enables application providers to activate it asnetwork conditions dictate.

See also, U.S. patent and patent application Nos., each of which isexpressly incorporated herein by reference in its entirety: Ser Nos.09/735,675; 09/771,036; 09/778,999; 09/800,267; 09/811,566; 09/818,723;09/829,360; 09/844,075; 09/849,623; 09/858,387; 09/858,956; 09/887,906;09/930,827; 09/963,352; 10/142,267; 10/167,401; 10/177,741; 10/246,957;10/247,084; 10/426,037; 10/644,676; 10/754,866; 10/764,196; 10/898,594;10/928,584; 11/017,997; 11/033,524; 11/134,136; 11/176,838; 11/279,899;11/323,788; 11/331,787; 11/338,534; 11/440,531; 11/492,610; 11/570,005;11/759,762; 11/958,929; 12/144,536; 12/237,151; 12/298,533; 12/329,702;12/412,790; 12/434,167; 12/441,595; 12/453,170; 12/557,479; 12/592,238;12/619,334; 12/648,685; 12/661,468; 12/696,760; 12/843,858; 12/915,418;12/963,484; 12/964,735; 12/996,375; 12/996,563; 13/065,038; 13/126,873;2003/0236087; U.S. Pat. Nos. 5,642,155; 5,721,815; 5,745,480; 5,790,549;5,828,737; 5,936,949; 5,956,337; 5,970,068; 6,006,069; 6,016,311;6,028,843; 6,061,562; 6,088,335; 6,101,174; 6,112,056; 6,230,005;6,240,274; 6,246,713; 6,307,836; 6,363,074; 6,370,391; 6,377,561;6,381,289; 6,556,820; 6,661,781; 6,683,866; 6,693,887; 6,741,575;6,757,268; 6,769,089; 6,771,660; 6,785,252; 6,804,521; 6,842,437;6,847,633; 6,850,732; 6,912,393; 6,956,834; 6,963,730; 6,985,455;7,016,375; 7,020,472; 7,106,781; 7,119,614; 7,130,283; 7,133,395;7,190,683; 7,218,936; 7,293,223; 7,299,064; 7,443,814; 7,486,639;7,529,193; 7,548,529; 7,656,845; 7,672,309; 7,684,807; 7,809,403;7,860,076; 7,899,463; 7,916,816; 7,925,211; 8,027,298; Re. 42,225; Re.42,788.

For example, the following initiators can activate bandwidth-on-demand:

1. Device initiated bandwidth-on-demand: The device monitors initiatesbandwidth-on-demand by monitoring the use of the device. Examples ofwhich are:

a. Tethering: The device detects that it is used as an access point or amodem. Upon detecting this mode, the device initiatesbandwidth-on-demand.

b. Uploading of data: The device detects that the subscriber isuploading a large data, and triggers bandwidth-on-demand for a fixedperiod of time.

c. Extension of the plan: The device monitors the consumed data rate,and initiates bandwidth-on-demand till the end of the current billingperiod.

2. Operator initiated bandwidth-on-demand: The operator, as a part of amarketing effort, or to market new services, provides the device abetter data rate. This can be done by designating the subscriber's dataas “gold” and enabling better QoS for the user's data for a fixed periodof time. Additionally, the user can also be allocated a higher number ofdata blocks (like more resource elements, and resource blocks, timeslots, or subcarriers).

3. Application driven bandwidth-on-demand: Applications, commonly termedas apps, when launched, detect the current data rate, and initiate abandwidth-on-demand. Examples of these are:

a. Live video/event streaming applications showing the latest sportevent

b. Video-on-Demand (VoD) applications like Hulu. These applications whenlaunched, detect the current data rate of the user, determine theoptimal data rate, and initiate a bandwidth-on-demand for the period ofthe video. These applications can also present the subscriber a choicefor viewing the content in a high definition mode with a guaranteedrate, or in standard definition mode, where the data rate might not beoptimal and the quality is not guaranteed.

c. Interactive gaming applications. Gaming applications determine theminimum QoS requirements, and initiate a bandwidth-on-demand in order tomeet the experience requirements for interactive gaming.

4. Sponsored bandwidth-on-demand: Sponsors and advertisements cansponsor additional throughput for a fixed period of time. Sponsorshipcan be tied within applications like live video/event streaming, VoDapplications, gaming.

5. Ask-Bid bandwidth-on-demand: The network based on the current stateof the network, provides options to the subscriber to bid for a higherthroughput for a fixed period of time. The subscriber bids for a certainthroughput rate, and the winning user is guaranteed the rate for a fixedperiod of time, or amount of data, or other limit or quantity.

6. Subscriber initiated bandwidth-on-demand: The subscriber initiates abandwidth-on-demand request, either for a fixed throughput, a fixedduration or a fixed amount.

Bandwidth-on-Demand Steps

Upon initiation, the process works as follows:

1. The initiator activates bandwidth-on-demand.

2. The device using the appropriate messaging protocol as per thestandard (for e.g. 3GPP LTE, 3GPP LTE-A, HSPA+, WCDMA, EV-DO, CDMA 2000)contacts the policy servers of the MNO.

3. The policy server contacts the Authentication, Authorization andAccounting (AAA) server in the MNO's core network.

4. The AAA server examines the BoD request, examines the credentials ofthe subscriber by contacting the billing server, and determines if therequest can be granted.

a. If the request can be granted, the AAA server contacts the policyserver.

b. The policy server contacts the scheduler on the serving basestation,which then determines to whether to allocate more resources (i.e.bandwidth in the form of subcarriers, resource blocks, resourceelements, timeslots) to the user. This will be measured as an increasein throughput for the user.

c. This action is communicated to the device, which initiates a timer ora data rate counter depending on the granted request.

5. If the AAA server determines that BoD cannot be granted to thesubscriber, either due to the current state of the network, or thesubscriber's credentials, the server notifies the policy server whichthen notifies the served device.

6. When either the determined time or the amount of data consumed isexhausted, the AAA server initiates the following actions:

a. It contacts the policy server.

b. The policy server drops the user to the original plan and initiatesappropriate actions with the scheduler of the serving base station.

Models for Bandwidth-on-Demand

Initiating bandwidth-on-demand successfully will result in increasedthroughput for the subscriber. Each initiator can have a certain model(e.g. fixed duration, as decided by the application, or bill/cost). Thefollowing table summarizes the models under which bandwidth-on-demandcan be delivered:

TABLE 1 Initiator Type Device initiated BoD Tethering 1. Fixed duration2. Cost Uploading of data 1. Fixed duration Extension of the plan 1.Fixed duration till the next billing cycle Operator initiated BoD 1.Fixed duration Application driven BoD Live event/video streaming 1.Fixed Duration Video-on-Demand 1. Fixed Duration Interactive Gaming 1.Cost 2. Until activity terminates Sponsored BoD 1. Price 2. FixedDuration Ask-Bid BoD 1. Fixed Duration Subscriber initiated BoD 1. FixedDuration 2. Price 3. Until user terminates Variable Pricing 1. Price forwhat is consumed

Measurement of Bandwidth-on-Demand

Dynamic bandwidth-on-demand allocation results in an increase ofthroughput. The throughput increase can be either duration based,cost/price based. The following methods can be used to measure thethroughput (determined over a period of time):

1. Average throughput

2. Min-Max measured throughput

3. Standard Deviation of the throughput (with respect to the mean)

4. Median throughput

Pricing for Bandwidth-on-Demand

Bandwidth-on-demand presents opportunities for several parties. Theoperator can monetize the investments in new technology effectively, andcan price services based on demand. Operators are now presented with ameans to market products that require small bursts of bandwidth. It alsopresents a means for sponsors to play a role in the data plans, andenable effective product placements during events. App (application)developers, game developers and content distribution networks canattractively price products based on the throughput requirements, andcan initiate BoD for delivering these products.

Effective Bandwidth-on-Demand

Bandwidth-on-Demand is a dynamic demand management idea, for currentMNOs. BoD can be used within the current network architectures.Nevertheless, there is a potential for further gains by pairing BoD withthe Shift and Add algorithm described below. The shift-and-add algorithmenables an operator to combine spectrum effectively, and to providehigher data rates with existing infrastructure. If the MNO has deployedshift-and-add, then the operator can effectively schedule BoDsubscribers on the other frequency carrier, thereby effectively freeingup the main frequency carrier to handle other subscribers.

Another aspect of the present technology provides a system whichdigitally formats data in a plurality of bands, each band beingseparately formed as a modulated signal, which are then transmittedusing a common broadband power amplifier. The modulated signals are, forexample OFDM modulated, though the modulation scheme may be different,and indeed the modulation scheme of the respective modulated signals maydiffer. A technique is used, for example, to ensure that the power peaksof the respective modulated signals are not aligned in time, thusreducing the PAPR, for example through a transform which maintains theinformation communication capacity of the band, maintains compatibilitywith legacy equipment users of the respective band. The modulatedsignals are coordinated to communicate portions of a singlecommunication, effectively providing a higher bandwidth communication.

Thus, at the transmitter, a digital processor divides a digital datastream between the various digital modulators. Typically, the dataprocessor and digital modulators are not responsive to the various datacodes and their possible modulated representations and resultant PAPR.However, in some embodiments, the digital processor is coordinated toproduce signals which convey the information stream, but avoidsimultaneous high power peaks in the various modulated signals, orprovide complementary peaks which destructively interfere.

In a particular embodiment, the modulated signals are digitallyprocessed after up-conversion, and shifted in time sufficient to avoidconstructive interference of power peaks, in a manner compatible withthe communications protocol.

At the receiver, typically a multiple concurrent band radio is employed,which captures the plurality of modulated signals through a singleantenna, low noise amplifier, downconverter, and digitizer, and thedigitized wideband signal is then digitally processed to extract anddecode the multiple modulated signals. Of course, it is also possible todemodulate the modulated signals with a plurality of radios.

Typically, the bands containing the modulated signals will be near eachother, e.g., within 100 MHz, and perhaps spaced 5, 10 or 20 MHz apart.In some cases, adjacent bands are licensed to different parties, but maybe transmitted from a common tower, e.g., cell site. The licensees(carriers) may employ different standards and protocols. One aspect ofthe present system permits various carriers to “borrow” bandwidth fromeach other, or permits users to aggregate bandwidth from multiplecarriers, without creating incompatibilities.

When multiple radio signals with different carrier frequencies arecombined for transmission, this combined signal typically has anincreased peak-to-average power ratio (PAPR), owing to the possibilityof in-phase combining of peaks, requiring a larger radio-frequency poweramplifier (PA) operating at low average efficiency. The PAPR for digitalcombinations of orthogonal frequency-domain multiplexed (OFDM) channelsmay be reduced by storing the time-domain OFDM signals for a givensymbol period in a memory buffer, and carrying out cyclic time shifts ofat least one OFDM signal, in order to select the time-shiftcorresponding to reduced PAPR of the combined multi-channel signal. Thismay be applied to signals either at baseband, or on upconverted signals.Simulations show that several decibels reduction in PAPR can be obtainedwithout degrading system performance. No side information needs to betransmitted to the receiver.

A preferred embodiment of the present system and method seeks to controlthe PAPR by storing the time-domain OFDM signals for a given symbolperiod in a memory buffer, and carrying out cyclic time shifts of atleast one of the OFDM signals, in order to select the time-shiftcorresponding to a desired PAPR of the combined multi-channel signal. Inmost cases, it would be desired to reduce the PAPR to a minimum, butthis is not a limitation of the technique, and the selected time-shiftmay be based on other criteria.

It is noted that each of the OFDM signals may be preprocessed inaccordance with known schemes, and thus each may have been themselvesprocessed to reduce an intrinsic PAPR, though preferably anypreprocessing of the signals is coordinated with the processing of thecombined signals to achieve an optimum cost and benefit. For example,where two separate signals are to be combined, each having a high PAPR,a resulting signal of reduced PAPR can be achieved if the peaks add outof phase, and thus cancel. Therefore, initial uncoordinated efforts tomodify the input OFDM signals may have limited benefit.

It is noted that the present system seeks to combine independentlyformatted OFDM, which are generally targeted to different receivers orsets of receivers, and these sets are typically not coordinated witheach other. For example, in a cellular transceiver system, a basestation may serve hundreds or thousands of cell phones, each phonemonitoring a single OFDM broadcast channel, with the base stationservicing multiple OFDM channels. It is particularly noted that each setof OFDM subcarriers is orthogonal, but the separate OFDM signals, andtheir subcarriers, are generally not orthogonal with each other. TheOFDM signals may be in channels which are adjacent or displaced, andtherefore a relative phase change between OFDM signals can occur duringa single symbol period. Therefore, the PAPR must be considered over theentire symbol period.

Indeed, according to another embodiment of the method, it is not thePAPR of the signal which is analyzed for optimization, but rather aninferred error at the receiver. This, if the PAPR of the compositesignal is high for only a small portion of a symbol period, such thatthe PA distorts or clips the signal at that time, but at most othertimes the combined signals are well within specification, the result maybe an acceptable transmission which would likely result in a low errorprobability. Indeed, in some cases, the error probability may be lowerthan for signals with a lower absolute peak. Therefore, by employing amodel of a receiver, which itself may include margins for specificcommunication channel impairments to specific receivers, and Dopplershifts (which may be determined, for example by analyzing return pathcharacteristics), or over a range of possible variation, as part of thetransmitter signal processing path, better performance may be availablethan by simply minimizing the PAPR.

Another option is to modify the OFDM signal during all or a portion ofthe period in a manner which deviates from a standard protocol, whichis, for example an IEEE-802 OFDM standard, WiFi, WiMax, DAB, DVB,cellular communication, LTE signal, or the like, but which does notsubstantively increase a predicted BER of a standard or specificreceiver. For example, if the PAPR is high for a small portion a symbolperiod, such that if during a portion of the symbol period, one or moresubcarriers were eliminated or modified, the PAPR would be acceptable,and the signal at the receiver would have sufficient information to bedecoded using a standard receiver without significant increase in BER,then the transmitter could implement such modifications without need totransmit side information identifying the modifications which necessaryfor demodulation. Another possible deviation is, for example, tofrequency shift the signal (which mildly violates the orthogonalitycriterion), within the tolerance of a receiver to operate within a rangeof Doppler shifts which are equivalent to frequency shifts.

Consider two OFDM signals that are being combined as in FIG. 2. Forsimplicity, call Signal 1 (S1) the reference signal, and Signal 2 (S2)the modified signal. During each OFDM symbol period, the basebanddigital data bits for each signal will be stored in memory. Assume thatthe Preamble has been stripped off, but the Cyclic Prefix CP remains. Asindicated in FIG. 3 for one embodiment of the invention, the bits forthe reference signal S1 are stored in a first-in-first-out (FIFO) shiftregister (SR). The corresponding bits for the modified signal S2 arestored in a circular shift register (CSR), so configured that the datacontained can be rotated under program control. The data for bothsignals are first up-converted to an intermediate frequency (IF) andthen combined (added), while maintaining digital format at a samplingfrequency increased over the digital data rate. The combined IF signalsare then subjected to a PAPR test, to determine whether the peak powerlevel is acceptable, or, in other embodiments, whether other criteriaare met. This might correspond, for example, to a PAPR of 9 dB. If thetest is passed, then the data bits for the combined OFDM symbols areread out, to be subsequently reassembled into the full OFDM frame andup-converted to the full RF, for further amplification in the PA andtransmission. According to another embodiment, a combined OFDMrepresentation of the combined data is itself the source for theup-conversion.

More generally, once the parametric transformation (relative time-shift)to achieve the desired criteria is determined, the final signal is thenformulated dependent on that parameter or a resulting representation,which may be the digital data bits of the baseband signal or a convertedform thereof; in the latter case, the system may implement a series oftransformations on the data, some of which are redundant or failed,seeking an acceptable one or optimum one; once that is found, it may notbe necessary to repeat the series or transformations again Likewise, theoption of reverting to the original digital data and repeating thedetermined series of transformations allows a somewhat differentrepresentation to be formed in the register, for example one which issimplified or predistorted to allow consideration of analog componentperformance issues in the combining test.

Even more generally, the technique provides that each signal to becombined is provided with a range of one or more acceptable parameters,which may vary incrementally, algorithmically, randomly, or otherwise,and at least a portion of the possible combinations tested and/oranalyzed for conformity with one or more criteria, and thereafter thecombination of OFDM signals implemented using the selected parameter(s)from a larger set of available parameters. This parametric variation andtesting may be performed with high speed digital circuits, such assuperconducting logic, in a serial fashion, or slower logic withparallelization as necessary, though other technologies may be employedas appropriate and/or necessary, including but not limited to opticalcomputers, programmable logic arrays, massively parallel computers(e.g., graphic processors, such as nVidia Tesla® GPU, ATI Radeon R66,R700), and the like. The use of superconducting digital circuits may beadvantageous, for example, where a large number of complex computationswhich make significant use of a specialized high speed processor, suchas where a large number of independent receivers are modeled as part ofa transmitter optimization.

In the preferred embodiment, at any state of the tests over theparametric range, if the test is not passed, a control signal is fedback to the register, e.g., CSR, which rotates the data bits of themodified signal S2. The shifted data is then combined with the initialstored data from S1 as before, and the PAPR re-tested. This is repeateduntil the PAPR test is passed. A similar sequence of steps isillustrated in FIG. 4, where stripping off the preamble and reattachingit at the end are explicitly shown. It is noted that, in some cases, thetests may be applied in parallel, and therefore a strictly iterativetest is not required. This, in turn, permits use of lower speed testinglogic, albeit of higher complexity. Likewise, at each relativetime-shift, a secondary parameter may also be considered.

For example, a secondary consideration for optimal combining may bein-band (non-filterable) intermodulation distortion. Thus, at each basicparametric variation, the predicted in-band intermodulation distortion,expressed, for example, as a power and/or inferred BER, may becalculated. This consideration may be merged with the PAPR, for example,by imposing a threshold or optimizing a simple linear combination “costfunction”, within an acceptable PAPR range.

While there may be some delays in this Shift-and-Add process (SAA), thetime for the entire decision algorithm, including all iterations, mustnot exceed the expanded symbol time T+ΔT. We have described a serialdecision process in FIGS. 3 and 4. As discussed, above, in some cases,it may be preferable to carry out parts of this process in parallel,using multiple CSRs with different shifts and multiple parallel PAPRtests, in order to complete the process more quickly. This isillustrated in FIG. 5, which suggests parallel memories (shown here asRAMs), each with an appropriate time shift, where the minimum PAPR isselected to send to the RF subsystem. The optimum tradeoff betweencircuit speed and complexity will determine the preferred configuration.

In some situations, the search for an optimum combined signal requiresvast computational resources. In fact, heuristics may be available tolimit the search while still achieving an acceptable result. In the caseof a PAPR optimization, generally the goal is to test for limited, lowprobability “worst case” combinations of symbols. If the raw digitaldata is available, a lookup table may be employed to test for badcombinations, which can then be addressed according to a predeterminedmodification. However, for multi-way combinations of complex symbolsthis lookup table may be infeasible. On the other hand, the individualOFDM waveforms may each be searched for peaks, for example 6 dB abovemean, and only these portions of the signal analyzed to determinewhether there is a temporal alignment with the peaks of other OFDMsignals; if the peaks are not temporally synchronized, then apresumption is made that an unacceptable peak will not result in thefinal combined signal. This method makes a presumption that should bestatistically acceptable, that is, that only portions of an OFDMwaveform that are themselves relative peaks will contribute to largepeaks in the combination of OFDM signals. This method avoids serialtesting of sequential parametric variations, and rather simply avoidsworst case superpositions of a binary threshold condition.

It is important to note that the circularly shifted symbol data for themodified signal represents exactly the same set of symbols as theunshifted data. Further, because of the standard properties of OFDMsignals, the shifted symbol set can be transmitted and received with nospecial side-information, and with no degradation of signal integrity.So the combined OFDM channels with reduced PAPR should exhibitessentially the same performance as the original unshifted version. Aset of detailed simulations that confirm this are described in theDetailed Description section below.

Although these figures focus on the case of reducing PAPR for thecombination of two OFDM channels, this method is not limited to twochannels. Three or more channels can be optimized by a similar method ofcircular time shifts, followed by PAPR tests.

A simplified flowchart for the method of the invention is shown in FIG.10. The increased bandwidth specified in this flowchart may representany appropriate increase in Quality of Service. The usage threshold mayrepresent a predetermined level of excess usage, a defined time, or somecombination thereof. The time delay associated with periodic re-checkingthe usage may be a time interval such as one minute, which may also beassociated with an appropriate surcharge algorithm. It may also be muchfaster, enabling more efficient bandwidth utilization by reconfiguringcommunication channels based on dynamic variations in real-time datarequirements.

The block diagram of a mobile wireless communications system employingthe BoD method is shown in FIG. 11. Note that the request for anincrease in QoS may come from the mobile user, but it may alternativelybe initiated automatically by the basestation to maximize overallwireless capacity, or by the Mobile Network Operator (MNO). Note furtherthat the reconfiguration of the QoS may be applied to the mobiletransceiver and/or the basestation transceiver, on either the downlinkor the uplink.

It is therefore an object to provide a system, computer readable mediumstoring a nontransitory program for a programmable processor, and methodand for dynamically changing the QoS for a user of a cellular radiosystem, comprising: requesting an increase in quality of service from anormal level; authenticating the request; determining availability of anincreased quality of service for the user; initiating the increase inthe quality of service for the user of the cellular radio system;metering the usage of the increased quality of service by the user;charging an account for the usage of the increased quality of service bythe user; determining a metering threshold; and upon exceeding themetering threshold, reverting the quality of service to the normal levelor recommencing at least the metering, charging and determining andreverting or recommencing.

It is another object to provide a processor for dynamically changing theQoS for a user of a cellular radio system, comprising: an input portconfigured to receive a request for an increase in quality of servicefrom a normal level; at least one processor configured to authenticatethe request, define a metering threshold and upon exceeding the meteringthreshold, to deauthorize the request, and to charge an account for theusage of the increased quality of service by the user; and an outputport configured to query a transceiver control server to determineavailability of an increased quality of service for the user, and ifavailable to initiate the increase in the quality of service for theuser of the cellular radio system and meter the usage of the increasedquality of service by the user.

The requesting may be initiated by a user, a cellular carrier, asponsor, and/or an application program executing on a cellular handset.

The increase in quality of service may comprise an increase in availablebandwidth in a communication band, and/or an increase in availablebandwidth in a plurality of communication bands.

The determining availability of an increased quality of service for theuser may comprise communicating between a central policy server and acell site server.

The metering may comprise timing a duration of increased quality ofservice, determining a quantity of data communicated, and/or determininga statistical measure of quality of service.

The charging may comprise charging a predetermined fixed amount for anincrement of increased quality of service, a variable amount for anincrement of increased quality of service, a competitively determinedamount for an increment of increased quality of service, and/or anamount for an increment of increased quality of service determined basedon an auction.

The determining a metering threshold may comprise determining expirationof a timer.

The method may, upon exceeding the metering threshold, revert thequality of service to the normal level and/or at recommencing least themetering, charging and determining. It is also an object to provide amethod for dynamically adjusting transmission quality, comprising:receiving at least two streams of orthogonal frequency multiplexedsymbols for concurrent transmission by a transmitter having a non-lineardistortion as a function of signal magnitude; determining, prior totransmission, a plurality of possible superpositions of the at least twostreams of symbols with respectively different cyclic time shifts of arespective orthogonal frequency multiplexed symbol, and selecting atleast one cyclic time shift which results in a non-linear distortionhaving acceptable characteristics; and transmitting the at least twostreams of orthogonal frequency multiplexed symbols with a selectedcyclic time shift having the acceptable characteristics, as a superposedsignal through the transmitter having the non-linear distortion as afunction of signal magnitude.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B shows typical behavior of an orthogonal frequency-domainmultiplexed channel in the frequency and time domains.

FIG. 2 shows the combination of two OFDM channels in a transmitter usinga double-upconversion method.

FIG. 3 provides a simple block diagram showing how two OFDM channels maybe combined, wherein the data bits of one OFDM channel may be cyclicallyshifted in order to reduce the peak-to-average power ratio (PAPR).

FIG. 4 shows the structure of two OFDM channels, with cyclic shifting ofthe data for one channel in order to reduce the PAPR.

FIG. 5 provides a block diagram showing memory storage of multipleshifted replicas of data from an OFDM channel, with selection of onereplica corresponding to minimizing the PAPR.

FIG. 6 shows a block diagram of a simulated communication system thatincorporates the shift-and-add algorithm in the transmitter.

FIG. 7 shows the transfer function of the Power Amplifier included inthe transmitter for the simulation shown in FIG. 6.

FIG. 8 plots the bit-error rate (BER) for the simulation usingquadrature phase-shift keyed (QPSK) OFDM signals, as a function of thesignal-to-noise ratio (SNR), with and without the Shift-and-Addalgorithm.

FIG. 9 plots BER using 16-quadrature-amplitude modulated signals(16-QAM) as a function of SNR, with and without the Shift-and-Addalgorithm.

FIG. 10 presents a flowchart for one preferred embodiment of the methodfor Dynamic Bandwidth-on-Demand.

FIG. 11 presents a block diagram of a mobile wireless system employingthe Bandwidth-on-Demand method.

FIG. 12 shows a schematic diagram of a prior art standard type computingsystem, which can be used to implement a programmable system accordingto the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present technology may be implemented by allocation to a user ofavailable bandwidth within a normal communication band, which istypically implemented by instructing the receiver, up to its capacity,to accept communications within the band, which may be designated bytimeslots, frames, codes, or the like. This is typically provided by asoftware “upgrade”, without requiring hardware modification. It is notedthat in some cases, a cellular handset or other radio has a data ratelimit imposed by hardware constraints, less than the full data rate forwhich a band is capable. Thus, the bandwidth on demand function istypically responsive to the receiver capability, which may differbetween a variety of receiver types. On the other hand, full to partialbackward compatibility with legacy receivers and protocols is notrequired, and therefore this is an optional feature.

Another implementation of the technology provides that the bandwidth isderived from multiple bands. In this case, the receiver may employmultiple radios, or a multiband receiver system. Advantageously, areceiver is provided which has broadband capability, and is capable ofsimultaneously receiving multiple bands within a block, through a singleantenna and low noise amplifier, and common down converter. This resultsin a wideband intermediate frequency (IF) modulated signal, representinga plurality of bands, which may be contiguous or discontiguous. Thereceiver may then provide various architectures for extracting theinformation. For example, a single high speed analog to digitalconverter could be provided to digitize the entire IF, and therepresentations of the multiple bands within the digitized IF signalthen digitally processed to extract the modulated information. On theother hand, the IF may then be further processed by a plurality oftuners, each reducing a respective band to baseband and filtering otherbands. This superheterodyne embodiment requires multiple receivingchannels, however, the parallel architecture elements operate atrelatively low speeds. Alternately, a plurality of subsampling analog todigital converters may separately process the IF signal, to selectivelydigitize the band of interest, which may then be digitally demodulated.

When a plurality of bands are bonded together to co-transmit a digitaldata stream, it is advantageous for these bands to be transmitted from acommon antenna, and received by a common antenna. Below is described indetail a method and apparatus for increasing the efficiency of thesystem by reducing the peak to average power ratio of a combined signal,while maintaining compatibility with typical cellular OFDM protocols. Inmany cases, the efficiency of the power amplifier in the transmitter isa significant factor, and by reducing the PAPR, an amplifier with lowerheadroom, and thus lower cost, higher efficiency, and/or greater averagepower may be employed.

OFDM channels are comprised of many sub-channels, each of which is anarrow-band signal (FIGS. 1A and 1B). An OFDM channel itself has atime-varying envelope, and may exhibit a substantial PAPR, typically9-10 dB. However, if two separate similar OFDM channels are combined,the resulting signal will exhibit PAPR of 12-13 dB, for a gain of 3 dB.This is unacceptably large, since it would require a power amplifierwith 4 times the capacity to transmit a combined signal that averagesonly 2 times larger.

A preferred embodiment therefore provides a PAPR reduction method whichreduces the PAPR of a two OFDM channel combined signal from 12-13 dBback down to the 9-10 dB of the original components. This ˜3 dBreduction in PAPR is preferably accomplished without degradation of thesignal, and without the need to transmit any special side informationthat the receiver would need to recover the OFDM symbols. Further, thealgorithm is simple enough that it can be implemented in any hardwaretechnology, as long as it is sufficiently fast.

Conventional methods of PAPR reduction focus on combining thesub-channels and generating a single OFDM channel without excessivePAPR. The present technique can be viewed in certain respects as acombination of Partial Transmit Sequence (PTM) and Selected Mapping(SLM).

In traditional PTS, an input data block of N symbols is partitioned intodisjoint sub-blocks. The sub-carriers in each sub-block are weighted bya phase factor for that sub-block. The phase factors are selected suchthat the PAPR of the combined signal is minimized.

In the SLM technique, the transmitter generates a set of sufficientlydifferent candidate data blocks, all representing the same informationas the original data block, and selects the most favorable fortransmission (lowest PAPR without signal degradation).

The present hybrid approach combines elements of PTS and SLM for summedcarrier modulated signals. The various cyclic time-shifts of theoversampled OFDM waveform are searched, and the time-shift with thelowest PAPR selected. One OFDM signal is used as reference and the othercarrier modulated signal(s) are used to generate the time-shifts, in amanner similar to PTS. The search window is determined by the cyclicprefix length and the oversampling rate.

While the phase space of possible combinations of shifts increasestremendously, it would not be necessary to explore all suchcombinations. In general, very high values of the PAPR occur relativelyrarely, so that most time shifts starting with a high-PAPR state wouldtend to result in a reduction in PAPR. Shifts in multiple channels couldbe implemented sequentially or in parallel, or in some combination ofthe two. Thus, for example, any combination with a PAPR within anacceptable range is acceptable, any unacceptable PAPR states occur 1% ofthe time, the search space to find an acceptable PAPR would generally be<2% of the possible states. On the other hand, if other acceptabilitycriteria are employed, a larger search space may be necessary orappropriate. For example, assuming that there is a higher cost fortransmitting a higher PAPR signal, e.g., a power cost or an interferencecost, then a formal optimization may be appropriate. Assuming that noheuristic is available for predicting an optimal state, a full search ofthe parametric space may then be appropriate to minimize the cost.

This differs from conventional approaches, wherein different OFDMchannels are independent of one another, with separate transmit chainsand without mutual synchronization. Further, the conventional approachesoperate directly on the baseband signals. In contrast, the presentmethod evaluates PAPR on an up-converted, combined signal thatincorporates two or more OFDM channels, and the symbol periods for eachof these channels must be synchronized. This will not cause problems atthe receivers, where each channel is received and clocked independently.

Some conventional approaches to PAPR are based on clipping, but theseinevitably produce distortion and out-of-band generation. Some otherapproaches avoid distortion, but require special transformations thatmust be decoded at the receive end. These either require sendingside-information, or involve deviations from the standard OFDMcommunication protocols. The present preferred approach has neithershortcoming.

OFDM channels used in cellular communications, may be up to 10 or 20 MHzin bandwidth. However, these channels might be located in a much broaderfrequency band, such as 2.5-2.7 GHz. So one might have a combination oftwo or more OFDM channels, each 10 MHz wide, separated by 100 MHz ormore. A 10 MHz digital baseband signal may be sampled at a rate as lowas 20 MS/s, but a combined digital signal covering 100 MHz must besampled at a rate of at least 200 MS/s.

In a preferred embodiment, the signal combination (including theup-conversion in FIG. 3) is carried out in the digital domain at such anenhanced sampling rate. The PAPR threshold test and CSR control are alsoimplemented at the higher rate. This rate should be fast enough so thatmultiple iterations can be carried out within a single symbol time(several microseconds).

In order to verify the expectation that the circular time-shift permitsreduction in PAPR for combined OFDM channels, without degrading systemperformance, a full Monte-Carlo simulation of OFDM transmission andreception was carried out. The block diagram of this simulation issummarized in FIG. 6, which represents the “SAA Evaluation Test Bench”,and shows a transmitter that combines OFDM signals at frequencies F₁ andF₂, subject to the SAA algorithm for PAPR reduction. At the receive end,this is down-converted and the signal at F₂ is recovered using astandard OFDM receiver. Along the way, appropriate Additive WhiteGaussian Noise (AWGN) is added to the channel. The simulation alsoincludes a realistic transfer function for an almost-linear PowerAmplifier (PA), showing deviation from linearity near saturation (seeFIG. 7). The gain factor does not matter for this simulation, so thiswas not included.

In these simulations, the PAPR of the OFDM signals at F1 and F2 aretypically 9-10 dB, and these are then added together to yield a combinedsignal with a typical PAPR of 12-13 dB. To minimize nonlinear distortionin the transmitted signal, the input power backoff (in dB) for theoperation of the transmitter PA is selected to be equal to the PAPR forthe combined signal. For each selected value of AWGN, the SNR (in dB) iscalculated based on the average powers of the noise and the signal. Thenthe simulation is run and the bit-error-rate (BER) obtained from thedigital signal reconstruction in the OFDM receiver. After application ofthe SAA, the PAPR is reduced, typically by up to 3 dB, to obtain amodified combined signal with PAPR of 9-10 dB. The input power backoffis then reduced to the new value of the PAPR, and the BER vs. SNR valuesresimulated.

The parameters for the PAPR bit-error-rate (BER) simulations include thefollowing. Each packet contains 800 bytes of information, which ismodulated over several OFDM symbol periods, depending on the modulationtype used. Both QPSK (quadrature phase-shift keying) and 16-QAM(16-quadrature amplitude modulation) are examined. Each SNR point is rununtil 250 packet errors occur. The cyclic prefix is set to ⅛ of thetotal symbol time. Carriers at frequencies F₁ and F₂ are spacedsufficiently that their spectra do not overlap. The oversampling rate isa factor of 8. Finally, a raised cosine filter was used, with a verysharp rolloff, with a sampling frequency F_(s)=160 MHz, and a frequencycutoff F_(c)=24 MHz. A PAPR threshold of about 9 dB for the combinedOFDM channels was used.

FIG. 8 shows the BER performance, as a function signal-to-noise ratio(SNR) (i.e., varying the AWGN power), with and without application ofthe SAA algorithm, for QPSK modulation. FIG. 9 shows the correspondinganalysis for 16-QAM. In both cases, there is very little degradation inBER from zero-shift curves. In FIGS. 8 and 9, the dashed line representsthe BER vs. SNR for the combined signal without modification, while thesolid line represents the BER vs. SNR for the combined signal after PAPRreduction using SAA. In FIG. 9 for 16QAM, the two lines are virtuallyindistinguishable. Thus, we have confirmed in these cases that thereduction in PAPR produced by SAA is not accompanied by an increase insignal distortion, and therefore that the SAA improves the systemtransmission efficiency by the full amount of the PAPR reduction, withno significant degradation in system performance. We further expectsimilar results (reduction in combined PAPR without signal degradation)to hold for combinations of three or more OFDM signals.

Analyzed quantitatively, the net performance improvement using the SAAis 2.35 dB for QPSK and 2.9 dB for 16-QAM, as inferred from the BERplots. For example, if without SAA, the BER exhibits an error floor of0.03 at an input backoff (for the PA) of 8.5 dB, whereas the BERexhibits the same error floor with SAA of 6.5 dB, the performanceimprovement will be 8.5−6.5=2 dB.

These simulations have confirmed not only that the SAA algorithm permitsreduction of PAPR in combined OFDM channels by ˜3 dB, but also that thisreduction is achieved without signal degradation and without the need tosend any special side information on the transformations in the transmitsignal.

One preferred implementation of the technique involves using a fastfield-programmable gate array (FPGA) with blocks for shift-registermemories, digital up-conversion, and threshold testing. Alternatively,an ultrafast digital technology, such as rapid-single-flux-quantum(RSFQ) superconducting circuits, may be employed. As the number of OFDMchannels being combined is increased, one needs either to increase thealgorithm speed, or alternatively carry out a portion of the processingin parallel.

This method may also be applied to a reconfigurable system along thelines of cognitive radio, wherein the channels to be transmitted may bedynamically reassigned depending on user demand and available bandwidth.Both the number of transmitted channels and their frequency allocationmay be varied, under full software control. As long as all channelsfollow the same general symbol protocol and timing, one may apply asimilar set of Shift-and-Add algorithms to maintain an acceptable PAPRfor efficient transmission.

The method of the present invention is illustrated by the flowchart ofFIG. 10. Here the request for a change in bandwidth is initiated, e.g.,by the mobile customer. This request is passed along to an appropriateautomated server, such as the AAA Server (Authentication, Authorization,and Accounting) of the Mobile Network Operator. This server confirmsthat the request is authentic, and determines if the additionalbandwidth requested is available. If so, the increased bandwidth isinitiated, and the additional usage is metered. An appropriate usagethreshold is pre-defined, and the cumulative usage is periodicallycompared to this threshold. This periodic checking may be made on atimescale of one minute, for example, or it may be significantly faster.Once the cumulative usage exceeds the threshold, the increased bandwidthis terminated, reducing the usage rate to the default value. The totalsurcharge for the increased bandwidth is computed and added to thecustomer's bill.

A block diagram for a hardware system that may implement the method ofFIG. 10 is shown in FIG. 11. This shows a mobile unit linked via a radioconnection with a cellular basestation, which in turn is linked to aserver in the Core Network of the Mobile Network Operator (MNO). Therequest for an increase in the Quality of Service may come from themobile user, and is passed via the mobile transceiver to the basestationand the MNO Core Network. Both the mobile transceiver and thebasestation transceiver have dynamic QoS control units, which can bereprogrammed remotely. Both uplink and downlink data communicationsrates may be adjusted. After the AAA Server in the Core Networkauthorizes a change, the scheduling processor in the basestationinitiates the change in the Dynamic QoS Control Unit of the mobileand/or the basestation transceiver. The Scheduling Processor also keepstrack of the cumulative usage, and determines when the QoS enhancementshould be terminated. The AAA Server receives the total usageinformation and computes the customer surcharge.

The example presented in FIG. 11 is one embodiment of a system that mayimplement the method of the invention, and should not be viewed aslimiting.

Hardware Overview

FIG. 12 (see U.S. Pat. No. 7,702,660, issued to Chan, expresslyincorporated herein by reference), shows a block diagram thatillustrates a computer system 400 upon which an embodiment of theinvention may be implemented. Computer system 400 includes a bus 402 orother communication mechanism for communicating information, and aprocessor 404 coupled with bus 402 for processing information. Computersystem 400 also includes a main memory 406, such as a random accessmemory (RAM) or other dynamic storage device, coupled to bus 402 forstoring information and instructions to be executed by processor 404.Main memory 406 also may be used for storing temporary variables orother intermediate information during execution of instructions to beexecuted by processor 404. Computer system 400 further includes a readonly memory (ROM) 408 or other static storage device coupled to bus 402for storing static information and instructions for processor 404. Astorage device 410, such as a magnetic disk or optical disk, is providedand coupled to bus 402 for storing information and instructions.

Computer system 400 may be coupled via bus 402 to a display 412, such asa liquid crystal display device (LCD), for displaying information to acomputer user. An input device 414, including alphanumeric and otherkeys, is coupled to bus 402 for communicating information and commandselections to processor 404. Another type of user input device is cursorcontrol 416, such as a mouse, a trackball, or cursor direction keys forcommunicating direction information and command selections to processor404 and for controlling cursor movement on display 412. This inputdevice typically has two degrees of freedom in two axes, a first axis(e.g., x) and a second axis (e.g., y), that allows the device to specifypositions in a plane.

The invention is related to the use of computer system 400 forimplementing the techniques described herein. According to oneembodiment of the invention, those techniques are performed by computersystem 400 in response to processor 404 executing one or more sequencesof one or more instructions contained in main memory 406. Suchinstructions may be read into main memory 406 from anothermachine-readable medium, such as storage device 410. Execution of thesequences of instructions contained in main memory 406 causes processor404 to perform the process steps described herein. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions to implement the invention. Thus,embodiments of the invention are not limited to any specific combinationof hardware circuitry and software.

The term “machine-readable medium” as used herein refers to any mediumthat participates in providing data that causes a machine to operationin a specific fashion. In an embodiment implemented using computersystem 400, various machine-readable media are involved, for example, inproviding instructions to processor 404 for execution. Such a medium maytake many forms, including but not limited to, non-volatile media,volatile media, and transmission media. Non-volatile media includes, forexample, optical or magnetic disks, such as storage device 410. Volatilemedia includes dynamic memory, such as main memory 406. Transmissionmedia includes coaxial cables, copper wire and fiber optics, includingthe wires that comprise bus 402. Transmission media can also take theform of acoustic or light waves, such as those generated duringradio-wave and infra-red data communications. All such media must betangible to enable the instructions carried by the media to be detectedby a physical mechanism that reads the instructions into a machine.

Common forms of machine-readable media include, for example, hard disk,magnetic tape, or any other magnetic medium, a DVD-ROM, any otheroptical medium, a RAM, a PROM, and EPROM, a FLASH-EPROM, ferroelectricmemory, any other memory chip or cartridge, or any other medium fromwhich a computer can read.

Various forms of machine-readable media may be involved in carrying oneor more sequences of one or more instructions to processor 404 forexecution. For example, the instructions may initially be carried on amagnetic disk of a remote computer. The remote computer can load theinstructions into its dynamic memory and send the instructions over atelephone line using a modem. A modem local to computer system 400 canreceive the data on the telephone line and use an infra-red transmitterto convert the data to an infra-red signal. An infra-red detector canreceive the data carried in the infra-red signal and appropriatecircuitry can place the data on bus 402. Bus 402 carries the data tomain memory 406, from which processor 404 retrieves and executes theinstructions. The instructions received by main memory 406 mayoptionally be stored on storage device 410 either before or afterexecution by processor 404.

Computer system 400 also includes a communication interface 418 coupledto bus 402. Communication interface 418 provides a two-way datacommunication coupling to a network link 420 that is connected to alocal network 422. For example, communication interface 418 may be anintegrated services digital network (ISDN) card or a modem to provide adata communication connection to a corresponding type of telephone line.As another example, communication interface 418 may be a local areanetwork (LAN) card to provide a data communication connection to acompatible LAN. Wireless links may also be implemented. In any suchimplementation, communication interface 418 sends and receiveselectrical, electromagnetic or optical signals that carry digital datastreams representing various types of information.

Network link 420 typically provides data communication through one ormore networks to other data devices. For example, network link 420 mayprovide a connection through local network 422 to a host computer 424 orto data equipment operated by an Internet Service Provider (ISP) 426.ISP 426 in turn provides data communication services through the worldwide packet data communication network now commonly referred to as the“Internet” 428. Local network 422 and Internet 428 both use electrical,electromagnetic or optical signals that carry digital data streams.

Computer system 400 can send messages and receive data, includingprogram code, through the network(s), network link 420 and communicationinterface 418. In the Internet example, a server 430 might transmit arequested code for an application program through Internet 428, ISP 426,local network 422 and communication interface 418.

The received code may be executed by processor 404 as it is received,and/or stored in storage device 410, or other non-volatile storage forlater execution.

In this description, several preferred embodiments were discussed.Persons skilled in the art will, undoubtedly, have other ideas as to howthe systems and methods described herein may be used. It is understoodthat this broad invention is not limited to the embodiments discussedherein. Rather, the invention is limited only by the following claims.

What is claimed is:
 1. A method for dynamically changing the level ofquality of service (QoS) for a communication by a user of a cellularradio system, comprising: requesting an increase in a level of qualityof service for the communication from a normal level encompassing usageof bandwidth within a first cellular communication band; authenticatingthe request; determining availability of an increased level of qualityof service for the communication representing available bandwidth withina second cellular communication band; initiating the increase in thelevel of quality of service for the communication by modifying acommunication protocol of a cellular radio system to concurrently usebandwidth within the first cellular communication band and the bandwidthwithin the second cellular communication band; metering the usage of theincreased level of quality of service; automatically charging an accountby producing at least one signal with an automated processor for theusage of the increased level of quality of service; determining ametering threshold; and upon exceeding the metering threshold, revertingthe level of quality of service for the communication to the normallevel of quality of service or recommencing at least the metering,charging and determining.
 2. The method according to claim 1, whereinthe requesting is initiated by a user.
 3. The method according to claim1, wherein the requesting is initiated by a cellular carrier.
 4. Themethod according to claim 1, wherein the requesting is initiated by asponsor.
 5. The method according to claim 1, wherein the requesting isinitiated by an application program executing on a cellular handset. 6.The method according to claim 1, wherein the normal level of quality ofservice for the communication within the first cellular communicationband employs an orthogonal frequency division multiplexed signal, andthe increase in level of quality of service comprises employing at leasttwo distinct orthogonal frequency division multiplexed signals inseparate bands.
 7. The method according to claim 1, wherein the increasein level of quality of service comprises an increase in availablebandwidth in a plurality of communication bands, wherein the bands areadjacent bands, separated by a guard band.
 8. The method according toclaim 1, said determining comprises communicating between a centralpolicy server and a cell site server.
 9. The method according to claim1, wherein said metering comprises timing a duration of an increasedlevel of quality of service.
 10. The method according to claim 1,wherein said metering comprises determining a quantity of datacommunicated.
 11. The method according to claim 1, wherein said meteringcomprises determining a statistical measure of quality of service. 12.The method according to claim 1, wherein said charging comprisescharging a predetermined fixed amount for an increment of increasedlevel of quality of service.
 13. The method according to claim 1,wherein said charging comprises charging a variable amount for anincremental increase of level of quality of service.
 14. The methodaccording to claim 1, wherein said charging comprises charging acompetitively determined amount for an incremental increase of level ofquality of service.
 15. The method according to claim 1, wherein saidcharging comprises charging an amount for an incremental increase oflevel of quality of service determined based on an auction.
 16. Themethod according to claim 1, wherein said determining comprisesdetermining expiration of a timer.
 17. The method according to claim 1,wherein upon exceeding the metering threshold, the level of quality ofservice reverts to the normal level.
 18. The method according to claim1, wherein upon exceeding the metering threshold, at least the metering,charging and determining are recommenced.
 19. A processor fordynamically changing the quality of service (QoS) for a user of acellular radio system, comprising: an input port configured to receive arequest for an increase in quality of service from a normal level; atleast one processor configured to authenticate the request, define ametering threshold and upon exceeding the metering threshold, todeauthorize the request, and to charge an account for the usage of theincreased quality of service by the user; and an output port configuredto query a transceiver control server to determine availability of anincreased quality of service for the user over a normal quality ofservice level employing communications within a single cellular radiosystem communication band, to an enhanced quality of service levelemploying concurrent communications within at least two cellular radiosystem communication bands, and if available to initiate the increase inthe quality of service for the user of the cellular radio system andmeter the usage of the increased quality of service by the user.
 20. Amethod for dynamically changing the level of quality of service (QoS)for a communication by a user of a cellular radio system, comprising:determining a need for an increase in a bandwidth-dependent quality ofservice level for a user of the cellular radio system from a firstquality of service level comprising communications within at least onecellular communication band to a higher second quality of service levelcomprising communications over the at least one cellular communicationband and at least one additional cellular communication band;determining availability of an increase in the quality of service forthe user of the cellular radio system from the first quality of servicelevel to the higher second quality of service level; initiating theincrease in the quality of service for the user of the cellular radiosystem by concurrently communicating, with the cellular radio system,portions of the communication over both the at least one cellularcommunication band and at least one additional cellular communicationband; charging an account for a metered amount of quantitative usage ofthe increase in the quality of service provided to the user of thecellular radio system; and upon exceeding the metered amount of increasein the quality of service provided to the user of the cellular radiosystem, at least one of: returning to the first quality of service, andinitiating and charging for a further metered amount of quantitativeusage of the increase in the quality of service, if determined to beavailable.